I. Field of the Invention
The present invention relates generally to the field of infinitely variable transmissions and, more particularly, to a continuously variable ratio transmission which is either manually or automatically controlled. The power is transmitted through gears which are fully engaged at all times. The invention also utilizes a planetary gear set as a power divider, which is also connected to a planetary gear set which acts as a power combiner.
II. Description of the Related Art
A typical vehicle transmission is shifted in specific and discrete steps between a high torque, low speed mode for when the vehicle is initially moved, and a high speed, low torque mode for when the vehicle is operating at normal highway speeds. In a case of a manual transmission, the shifting is accomplished by changing the engagement of various gears and gear sets. In an automatic transmission, the shifting is accomplished by controlling the engagement of various friction elements and their relationships to one another. Because of shifting in discrete steps, the efficiency of the operation is somewhat lacking. Obviously, the most efficient operation of a vehicle would be improved if the transmission could have continuously adjusted ratios to compensate for changing operating conditions.
Auto makers have attempted for many years to provide a continuously variable transmission which would allow high efficiency operation of an engine under high load conditions, especially when accelerating. The most successful continuously variable transmissions now being used are those which are belt-driven systems that adjust gear ratio through the use of variable diameter pulleys.
These belt driven transmissions have been plagued with relatively low time between overhaul, and by low reliability, due to excessive wear of the flexible belts connecting the pulleys. Current automatic automobile transmissions utilize hydraulics and soft clutches to transmit the power. Both the belt-driven transmissions and the current automatic transmissions dissipate energy and require substantial maintenance. In addition, other continuously variable transmission designs have been developed to include hydraulic designs and traction drives that rely on transfer of rotation by means of hydraulic fluid or by the interaction of adjacent rotating structures. Both of these types of drives, however, are currently unable to supply sufficient torque for automotive or heavy industrial use. Many of these types of designs are also load sensitive and are unable to drive vehicles having high loads.
In view of the above, there is a need for a reliable and durable continuously variable transmission that can be used to improve the versatility and operating efficiency of internal combustion engines. It is believed that the present invention will meet the need of such a transmission by providing dual power paths without the use of clutches or torque converters, and which will allow precise control of the shifting between the various power paths.